Some wireless communication devices, including wireless phones and wireless tablets, transmit and receive data wireless according to multiple protocols. These protocols can broadly be characterized as involving long range and short range communications. Wireless communication devices may perform short range (for example, less than 30 meters) communications according to a short range protocol such as the IEEE 802.11 (“802.11”) specification.
The 802.11 specification is more commonly known as “WiFi,” which is the commercial name for the standard. Most wireless local area networks (WLANs), which link two or more devices using a wireless distribution method, implement the 802.11 standard. Wireless signals transmitted according to the 802.11 specification propagate at a frequency of 2450 MHz (2.45 GHz).
Wireless signals produced according the 802.11 are characterized by a frequency that is within an ISM radio band. As indicated by the name, ISM radio bands are portions of the radio spectrum that are reserved internationally for the use of radio frequency (RF) energy for industrial, scientific and medical purposes, other than communications. Examples of applications in the ISM bands include radio-frequency process heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagpetic interference and disrupt radio communication using the same frequency. This is the reason that these ISM devices were limited to certain bands of frequencies.
Despite the intent of the original allocation, in recent years the fastest-growing uses of the ISM bands have been for short-range, low power communications systems such as WLAN communication according to the 802.11 standard. Additional communication systems that operate in the ISM band are cordless (non-mobile) phones, Bluetooth™ devices, and near field communication (NFC) systems. Generally speaking, communications equipment operating in the ISM band must tolerate interference generated by ISM equipment, and users have no regulatory protection from an ISM device.
However as it turns out, a bigger issue effecting WLAN communications relates to simultaneous wireless communications generated according to one or more long rang protocols. These long range protocols include standards promulgated by the 3rd Generation Partnership Project (3GPP), including “3G,” which is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. Other more recent long range protocols are the “4G” protocols which include the Worldwide Interoperability for Microwave Access (WiMAX) specification as well as the Long Term Evolution (LTE) standard.
The WiMAX specification is a commercial implementation of the IEEE 802.16 family of wireless-networks standards. The WiMAX standard provides for 30 to 40 megabit per second data rates over a range far surpassing the 30-meter wireless range of a conventional WLAN. Specifically, WiMAX signals are offered with a signal radius of about 50 km.
The LTE standard, which has been marketed as 4G-LTE, is a standard for wireless communication that was developed by the 3GPP, and is specified in the Project's Release 8 document series, with minor enhancements described in Release 9. The LTE standard for wireless data communications is an evolution of the Global System for Mobile Communications (GSM)/Universal Mobile Telecommunications System (UMTS) standards. The goal of the LTE standard was to increase the capacity and speed of wireless data networks using new digital signal processing techniques and modulations that were developed around the year 2000. A further goal was the redesign and simplification of the network architecture to an IP-based system with significantly reduced transfer latency compared to the 3G architecture.
As mentioned above, certain problems arise when a wireless communication device simultaneously processes a WLAN signal and a 3G or 4G LTE signal. The problems arise because the 3G and 4G LTE standards are implemented with signals having frequencies that border or overlap the ISM band within which WLAN (and Bluetooth™) signals propagate. Because of this overlap in signals, for example, when an LTE signal is transmitted by a device at an overlapping frequency, a simultaneously transmitted WLAN signal may be blocked from being received by the device. Additionally, when a signal is transmitted by the device over a WLAN, the signal may be intermodulated with an LTE signal being received by the device. What is needed therefore is a wireless communication device that can simultaneously process WLAN and LTE signals and can account for the overlap in the frequencies of the WLAN and LTE signals.